The given argument states that "dumping" is "selling a product in another country for less than production cost." It goes on to conclude that Country F is dumping shrimp because they are selling in Country G for less than Country G's production costs.
(A) is correct because it notes a point of ambiguity in the argument. The argument defines "dumping" as "selling a product in another country for less than production cost," but it does not clarify if "production cost" refers to the production cost of the country originating and selling the product or the production cost of the country that the product is being sold in. If "production cost" refers to the former, we would not have enough evidence to say that Country F is dumping because we have no information on the production costs of shrimp there. If "production cost" refers to the latter, then we could say Country F is dumping because we know their sale prices are below Country G's production prices.
(E) is incorrect because the distinction between selling "for considerably less than production cost or just slightly less" is irrelevant. The definition of "dumping" given in the argument only specifies "selling a product in another country for LESS than production cost." So, whether the Country F producers are significantly or only slightly underselling, it would still be considered dumping.
Does this make sense? Please let us know if you have additional questions!